1. Field of the Invention
The present invention relates to a liquid droplet ejecting apparatus for use in an ink jet printer or the like, and more specifically, to a liquid droplet ejecting apparatus with high level safety so that inadvertent ejection of ink is prevented in a hand-held type ink jet printer or the like.
2. Description of the Related Art
There has been utilized a thermal ink jet system in various types or printer (See JP 48-9622 A, JP 54-51837 A, etc.), in which partial evaporation of ink is rapidly effected through heating with a heater to thereby cause ink droplets to be ejected through nozzles by the expansion force, etc.
Further, a printer is known, which utilizes an ink jet that oscillates an oscillation plate by driving means such as static electricity or a piezoelectric element to thereby cause ink droplets to be ejected through nozzles by the oscillation energy (See JP 11-207956 A, JF 11-309850 A, etc.).
In ink jet printers described above, generally, an ink receiving member, namely a recording medium such as paper for recording, recording sheet, image receiving paper and image receiving medium (hereinafter represented by a recording sheet), is fed into the apparatus, and image recording is performed while conveying the member or medium.
For example, in a case of a printer using a so-called line head type ink jet recording head (hereinafter referred to as recording head), in which nozzles for ejecting ink are arranged beyond one side or the recording sheet, the recording head is stationary; the recording sheet is situated in a predetermined recording position; and an image is recorded on the entire surface of the recording sheet by continuously conveying (scan-conveying) the sheet in a direction perpendicular to the direction in which the nozzles are arranged.
In a case of a so-called serial type printer that is widely available, the recording sheet is intermittently conveyed at a predetermined pitch corresponding to the nozzle arrangement length, and, while the conveyance of the recording sheet is at rest, scanning is effected with the recording head in a direction perpendicular to the nozzle arrangement direction to perform image recording; by repeating the operation, an image is recorded on the entire surface of the recording sheet.
Further, an electronic stamp type ink jet printer is also known, which does not take in the recording medium such as a recording sheet but which is situated in a position corresponding to the recording medium to record an image.
For example, JP 3-261560 A discloses a planar printer in which the recording head (printer) main body on which nozzles are arranged in a matrix-like fashion (two-dimensionally) is placed on an arbitrary recording sheet, two-dimensional printing (image recording) being effected by ink jet.
In such an electronic stamp type printer, positioning is performed on the printer with respect to the recording sheet (recording medium) prior to image recording, whereby image recording (ejection of liquid droplets) is effected with the recording sheet facing the nozzles of the recording head.
Thus, unlike a printer which performs image recording while conveying a recording sheet taken therein, as is the case with the aerial type printer referred to above, this type of printer is advantageously capable of performing image recording without being restricted in terms of the size, configuration, thickness, rigidity (toughness or stiffness, for instance), etc. of the recording sheet. Further, since the recording object is not put into the printer, it is advantageously possible to employ various objects other than a recording Sheet, such as a wall and a three-dimensional object, as a recording medium and perform image recording thereon.
In this type of printer, such as an electronic stamp, ink is ejected into an open space, so that it is possible to eject ink onto an arbitrary location according to the position, situation, orientation, etc. of the printer positioned.
On the other hand, it can happen that ink is inadvertently ejected in unintended situations. For example, ink can be ejected before the recording head has been correctly opposed to the recording sheet. In such cases, ink can adhere to an object other than the image recording object, such as the skin or clothes of a person or a piece of furniture. Further, if it does not adhere to an object other than the recording object, ink sprayed into the air will, though not poisonous, undesirably pollute the environment.
The present invention has been made with a view toward solving the above problem in the prior art. It is an object of the present invention to provide a liquid droplet ejecting apparatus, which ejects liquid droplets with a modulation in response to a signal and is used in, for instance, such an ink jet printer as the above-mentioned electronic stamp, in which ink is ejected basically into an open space, which apparatus is of so high-level safety that it makes it possible to prevent liquid droplets from being inadvertently ejected when, for example, the liquid droplet ejecting head has not been correctly opposed to the object of liquid droplet ejection and to prevent consequently liquid droplets from adhering to an unwanted place or being sprayed into the air.
In order to attain the object described above, the first aspect of the invention provides a liquid droplet ejecting apparatus comprising an ejecting head having a plurality of nozzles for ejecting liquid droplets and a plurality of liquid droplet ejecting devices arranged in correspondence with the plurality of nozzles, respectively, and driven with modulation in response to signals, a detection unit for detecting a condition of a virtual surface opposed to the ejecting head, and a unit for prohibiting liquid droplet ejection from at least a part of the plurality of nozzles of the ejecting head depending on a result of detection by the detection unit.
In the liquid droplet ejecting apparatus, it is preferable that the detection unit is either a unit for detecting a human body, a unit for measuring a distance between an object existing in a liquid droplet ejection region for the plurality of nozzles of the ejecting head and the ejecting head, or a variation detection unit for detecting variations in a condition of a recording medium to be recorded existing in a liquid droplet election region for the plurality of nozzles of the ejecting head.
In order to attain the object described above, the second aspect of the invention provides a liquid droplet ejecting apparatus comprising an ejecting head having a plurality of nozzles for ejecting liquid droplets and a plurality of liquid droplet ejecting devices arranged in correspondence with the plurality of nozzles, respectively, and driven with modulation in response to signals, an angle detection unit for detecting an angle made by a direction, in which liquid droplets are ejected from at least a part of the plurality of nozzles of the ejecting head, and a preset reference direction, preferably, for instance, a vertical direction, and a unit for prohibiting liquid droplet ejection from at least a part of the plurality of nozzles of the ejecting head depending on an angle detected by the angle detection unit.
In the liquid droplet ejecting apparatus according to the first and second aspects of the invention, it is preferable that liquid droplets are ejected from the ejecting head into an open space.
It is also preferable that the liquid droplets are ink droplets, and wherein the liquid droplet ejecting apparatus is an ink jet printer.